1. Field of the Invention
This invention relates to radio base station receiving data transmission systems provided for uplink site diversity of mobile communication systems. This application is based on patent application No. Hei 9-174044 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally, one kind of site diversity receiving method is disclosed by the paper of Japanese Patent Application, Publication No. Hei 7-107033, for example. This method is used for improvements of the communication quality, which is realized such that the same signal from a mobile station is received by multiple base stations rather than by a single base station.
FIG. 8 shows an example of a network configuration according to the conventional site diversity receiving method.
In FIG. 8, a mobile station 130 is placed in communicating states with multiple base stations 230-1 to 230-L. Signals received by the base stations are subjected to selection and composition at a diversity composition node 220, an output of which is forwarded to a mobile communication network 210 and is then sent to a network 200 such as PSTN (an abbreviation for "Public Switched Telephone Network") or ISDN (an abbreviation for "Integrated Service Digital Network").
FIG. 9 shows an example of a frame format used between a radio base station and a base station control device in accordance with the conventional method.
In the case of the site diversity that performs communication using three radio base stations, it is necessary to provide three lines of a frame format 400, which consists of a frame number, error detection information, error frequency and receiving data. Herein, 335 bits are provided for one line, so it is necessary to provide a capability of transmitting 1,005 bits for three lines.
The aforementioned conventional technology suffers from the following problem.
In the site diversity, receiving data are transferred from the multiple radio base stations to the base station control device, wherein a diversity effect is obtained by selecting error-free data in the receiving data. In order to perform transfer of the receiving data from the multiple radio base stations to the base station control device, it is necessary to provide a number of lines, which corresponds to a number of radio base stations that are used to establish the site diversity between the radio base stations and base station control device. In the case of the uplink site diversity using three radio base stations, it is necessary to provide three lines, for example.
Because, each radio base station does not evaluate quality of the receiving data thereof, so it merely transmits correct receiving data as well as wrong receiving data to the base station control device.